Surface treatment of aluminum and aluminum alloys



Patented Apr. 24, 1951 UNITED STATE s PATENT OFFICE Eli Simon, Los Angeles, and Frederic M. Carasso,

Pasadena, craft Corporation,

Califi, assignors Burbank, "Calif.

No Drawing. Application May 12, 1945,

Serial No. 7

2 Claims.

This invention relates to the surface treatment of aluminum and aluminum alloys, and more particularly to the use of a non-ionic wettin agent in an anodizing bath for aluminum and its alloys.

It is an object of this invention to use a nonionic wetting agent in the anodizing bath that makes it possible to produce a porous, more adsorbent anodic oxide coating on aluminum and its alloys at a lower current density than could be used to produce the same coating under corresponding conditions Without the use of the wetting agent.

A further object of the invention is to produce in a short anodizing time, at ordinary temperature and at low current density, a thick, uniform and porous anodic coating.

In the preferred practice of this invention, the

aluminum article to be treated is first thoroughly cleaned, and then employed as the anode in the electrolysis of a sulfuric acid solution containing a non-ionic wettin agent.

The amount of sulfuric acid in the electrolyte may vary from 10% to by volume. A porous adsorbent oxide coating which satisfactorily retained dyes, was produced on'aluminum articles with a current density as low as one ampere per square foot of surface when approximately 0.1% by volume of the non-ionic wetting agent consisting of alkylated phenoxy polyethoxy ethanols was added to the electrolyte. The use of the non-ionic wetting agent in the anodizing bath also made it possible to produce anodic oxide coatings suitable for dyeing, that were thicker and had greater adsorptive powers than those producible under corresponding conditions, but without the effective wetting agent.

It was also found that by adding a non-ionic wetting agent in an aqueous solution of sulfamic acid, ammonium bisulphate, or other electrolyte in which it is stable, it was possible to produce a porous, adsorbent anodic oxide coating on aluminum at a lower current density than could be used to produce the same coating with the same electrolyte Without the wetting agent. But in experimenting with wetting agents, we discovered that neither the adding of the usual anion-active type, nor the adding of the cationactive type wettin agent in the anodizing bath had anyappreciable effect on the production of the anodic oxide coating on the aluminum article.

In practice, we prefer to employ the wetting agent known to the trade as Triton NE, it being understood that other s table non-ionic to Lockheed Air.-

wetting agents may be used. Triton NE is a non-ionic surface-active material consisting of iso octyl species of alkylated phenoxy polyethoxy ethanols. Good results were obtained when the electrolyte contained approximately 0.1% by volume of the wetting agent mentioned.

Although the use of the non-ionic wetting agent makes it possible to produce an oxide coating on the aluminum which satisfactorily retained dyes, at the low current density of one ampere per square foot of surface coated, the current density may, however, vary from one to twenty amperes per square foot, depending upon the dye to be used, the color intensity desired, the anodizing time, and the dyeing conditions. The voltage required for forming a thick, porous, adsorbent and otherwise satisfactory oxide coating on the aluminum article is approximately fourteen volts. The anodizing time may vary from ten to thirty minutes.

An important advantage of the process the anodizing bath room temperature, that is from about Fahrenheit to 100 Fahrenheit. In practice, the best results were obtained when the temperature of the anodizing bath ranged from Fahrenheit to Fahrenheit.

After the anodic treatment, the article is removed from the sulfuric acid bath and washed with water. It may then be dyed.

Having now particularly described the method of our invention and the improved results obtained thereby, what we claim is:

1. An electrolyte for the anodic oxidation of aluminum and alloys thereof to produce an absorbent coating, said electrolyte comprising an aqueous solution containing from 10% to 20% by volume of sulfuric acid, and approximately 0.1% by volume of a non-ionic wetting agent consisting of iso octyl species of alkylated phenoxy polyethoxy ethanols.

- 2. In a process of producing thick, porous,

is that absorbent oxide coatings on aluminum suitable for dyeing, the steps comprising using the article to be treated as the anode in an electrolytic cell, the electrolyte of which contains 10% to 20% by volume of sulfuric acid and 0.1% by volume of a non-ionic wetting agent consisting of iso octyl species of alkylated phenoxy polyethoxy ethanols. the temperature of said electrolyte ranging from 60 Fahrenheit to Fahrenheit, and impressing an electric current having an operating voltage of approximately fourteen volts and a current density of the order of from one may remain at ordinary- 3 4 to twenty amperes per square foot of surface on FOREIGN PATENTS said electrolytic cell for a period ranging from Number Country Date ten thlrty mmutes- 176,945 Switzerland July 16, 1935 ELI SIMON. FREDERIC M. CARASSO. 5 JREFERENGES CITED The following references are of record in the file of this patent:

OTHER REFERENCES S ier. No. 369,618, sassettiet lal. (A. P. 0.), published May 18, 1943.

Industrial and Engineerin Chemistry, Jan. .1941, pp. 17 thru 22.

10 Surface Active Substances, by Young and UNITED STATES PATENTS Coons, published in 1945, p. 110. Number Name Date Chemical Industries, Mar. 1943, pp. 326, 2,279,252 Slunder V Apr. 7, 1942 27 32g 2,320,999 Beebe .June 3, 1943 2,376,082 Pullen May-1-5,1945'15 

1. AN ELOCTROLYTE FOR THE ANODIC OXIDATION OF ALUMINUM AND ALLOYS THEREOF TO PRODUCE AN ABSORBENT COATING, SAID ELECTROLYTE COMPRISING AN AQUEOUS SOLUTION CONTAINING FROM 10% TO 20% BY VOLUME OF SULFURIC ACID, AND APPROXIMATELY 0.1% BY VOLUME OF A NON-IONIC WETTING AGENT CONSISTING OF ISO OCTYL SPECIES OF ALKYLATED PHENOXY POLYETHOXY ETHANOLS. 